Betta bellica Care Guide – Tank Setup, Feeding and Breeding

Quick summary

Betta bellica is a moderately challenging wild betta best suited to intermediate aquarists who can provide a heavily planted, soft and slightly acidic 75+ litre tank with a secure lid. It’s not a beginner fish or a bowl dweller, but if you can meet its water and space requirements, it’s a hardy, interactive species that also offers the reward of fascinating mouthbrooding behaviour.

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In this guide:

Introduction
Quick Stats
Appearance
Natural Habitat
Tank Size and Setup
Water Parameters
Filtration and Equipment
Diet and Feeding
Behaviour and Temperament
Tank Mates
Breeding
Common Diseases
FAQs

Introduction

Betta bellica is a wild-type betta species that stands apart from the commonly kept Betta splendens in both form and temperament. Known in the hobby as the Slim Betta or Slender Betta, this elegant fish belongs to a small species group that it shares with its close relative, Betta simorum. First described scientifically by Sauvage in 1884, Betta bellica has long fascinated aquarists who appreciate wild bettas for their subtler but no less captivating beauty. Its elongated, streamlined body and shimmering bronze-green iridescence make it a striking centrepiece for a well-planted aquarium, and its behaviour – particularly during courtship and spawning – offers a rewarding window into the natural world of anabantoid fishes.

Unlike the domesticated Betta splendens, which has been selectively bred for exaggerated finnage and vivid colouration, Betta bellica retains the understated elegance of a species shaped by its wild environment. It is larger than many of the more popular wild betta groups, such as the coccina complex, and its care requirements reflect the particular conditions of the clear, slow-moving streams it calls home in Peninsular Malaysia and Sumatra. While not a beginner’s fish, Betta bellica is well within the capabilities of an intermediate aquarist who is willing to research its needs and provide a suitably designed aquarium. This guide covers everything you need to know to keep and, potentially, breed this remarkable species successfully.

Quick Stats

Scientific name	Betta bellica
Common names	Slim Betta, Slender Betta, Betta bellica
Family	Osphronemidae
Origin	Peninsular Malaysia and Sumatra, Indonesia
Adult size	10-13 cm
Lifespan	3-5 years
Difficulty	Moderate
Breeding difficulty	Moderate
Temperature	22-28 °C
pH range	5.0-7.0
General hardness (GH)	2-8 dGH
Carbonate hardness (KH)	1-5 dKH
Minimum tank size	75 litres
Conservation status	Vulnerable (IUCN)

Appearance

Betta bellica is one of the more physically impressive wild betta species, owing to its relatively large size and sleek body shape. Adults typically reach between 10 and 13 cm in total length, making them considerably larger than many of the dwarf wild betta species that have become popular in recent years. The body is elongated and laterally compressed, giving the fish the streamlined silhouette that earned it the common name “Slim Betta.” The head is somewhat pointed, and the mouth is upturned – an adaptation shared with other surface-feeding anabantoids.

The base colouration of Betta bellica is a warm brown to olive-green, overlaid with a striking iridescent sheen that shifts between bronze, green, and occasionally blue-green depending on the angle of light. This iridescence is most pronounced along the flanks and gill covers, where it can appear almost metallic under good aquarium lighting. A series of dark horizontal stripes runs along the length of the body, though these can appear more or less prominent depending on the fish’s mood, health, and social context. When stressed or subdued, the stripes may become more visible, while a dominant, healthy individual in good condition often displays a richer, more uniform iridescence that partially obscures them.

The fins of Betta bellica are moderately sized relative to its body, lacking the extravagant flowing finnage of domesticated Betta splendens but possessing a graceful, functional elegance. The caudal fin is rounded to slightly spatulate, and the anal fin is elongated, tapering to a point in mature males. The dorsal fin is set well back on the body and is relatively short. Males are generally more colourful than females, displaying more intense iridescence and slightly more extended fin tips. Females tend to be somewhat plainer, with a more muted colouration and less pronounced fin extensions, though they can still show attractive green-bronze tones. Both sexes may display a dark spot or series of spots at the base of the caudal fin.

During courtship and aggressive displays, males intensify dramatically in colour. The iridescent green and bronze tones become vivid, the dark stripes may deepen, and the fins are spread wide to create an impressive display. This transformation is one of the great pleasures of keeping wild bettas and highlights the importance of providing conditions that allow the fish to feel secure enough to express its full range of colouration.

Natural Habitat

Betta bellica is native to the lowland regions of Peninsular Malaysia and the island of Sumatra in Indonesia. Its range spans several states in Malaysia, including Perak, Selangor, and Pahang, and extends into the north-eastern provinces of Sumatra. Within this range, it inhabits a variety of freshwater environments, though it shows a clear preference for clear, slow-moving streams and small rivers with dense marginal and aquatic vegetation.

The typical Betta bellica habitat is a shaded, gently flowing stream running through tropical forest or secondary growth. The water in these environments is generally soft and slightly acidic, influenced by the decomposition of leaf litter and other organic material that accumulates on the stream bed. However, unlike some of the blackwater-specialist wild bettas such as those in the coccina group, Betta bellica tends to be found in clearer water rather than heavily tannin-stained peat swamp environments. The substrate is usually sandy or composed of fine gravel, with a layer of fallen leaves and small branches providing cover and contributing to the water chemistry.

Vegetation plays a crucial role in the natural environment of Betta bellica. Dense stands of marginal plants overhang the water’s edge, providing shade and reducing light levels. Submerged and emergent aquatic plants – including species of Cryptocoryne, which are native to the same regions – offer additional cover and create the complex microhabitats that this species uses for foraging, shelter, and breeding. The water temperature in these habitats typically ranges from 22 to 28 degrees Celsius, though it can fluctuate seasonally and diurnally depending on the degree of canopy cover and the flow rate of the stream.

As a member of the family Osphronemidae, Betta bellica possesses a labyrinth organ that allows it to breathe atmospheric air. This adaptation is particularly valuable in the warm, oxygen-depleted conditions that can occur in slow-moving tropical streams, especially during the dry season when water levels drop and flow rates decrease. In the wild, Betta bellica can often be observed rising to the surface to take gulps of air, supplementing the oxygen it extracts from the water through its gills.

It is worth noting that Betta bellica is currently classified as Vulnerable by the IUCN, reflecting ongoing habitat loss throughout its range due to deforestation, agricultural expansion, and urban development. Aquarists who keep this species have a responsibility to source their fish from captive-bred stock where possible and to support conservation efforts aimed at preserving the freshwater habitats of Southeast Asia.

Tank Size and Setup

A single pair or small group of Betta bellica requires a minimum aquarium volume of 75 litres. Given the species’ relatively large adult size and its active, occasionally territorial nature, larger tanks of 100 litres or more are strongly recommended, particularly if you intend to keep a pair alongside other species or maintain a small group. A tank with a footprint of at least 60 cm x 30 cm provides adequate horizontal swimming space, which is more important for this species than height.

The aquarium setup should aim to replicate the key features of the species’ natural habitat: dense vegetation, subdued lighting, and plenty of cover. A dark substrate of fine sand or smooth gravel provides an aesthetically appropriate base and helps the fish feel secure, which in turn encourages the display of their best colouration. A layer of dried leaf litter – Indian almond leaves (Terminalia catappa) or oak leaves are both excellent choices – scattered across the substrate adds a naturalistic touch, releases beneficial tannins that gently soften and acidify the water, and provides surfaces for the growth of biofilm and microfauna that the fish will graze upon.

Planting should be dense, particularly around the perimeter and rear of the tank, with species that tolerate soft, slightly acidic water. Cryptocoryne species are ideal, being native to the same regions as Betta bellica and tolerant of the low to moderate light levels that suit this fish. Java fern (Microsorum pteropus), Anubias species, and various mosses such as Java moss (Taxiphyllum barbieri) are also excellent choices. Floating plants such as Salvinia, Limnobium, or Ceratopteris are highly recommended, as they reduce light intensity at the surface and provide the kind of overhead cover that makes Betta bellica feel most at ease.

Driftwood and pieces of bogwood serve dual purposes: they provide additional hiding spots and visual barriers, and they release tannins that contribute to the slightly acidic water chemistry this species prefers. Arrange the hardscape to create distinct territories and lines of sight, which helps to reduce aggression if more than one male is present. Terracotta pots, coconut shells, and PVC pipes can also be used as additional shelters, though natural materials tend to look more aesthetically pleasing in a biotope-style setup.

A tight-fitting lid is essential for Betta bellica. Like all anabantoids, this species is an accomplished jumper and will readily leap from an uncovered aquarium, particularly when startled or during aggressive encounters. Ensure there is a small gap between the water surface and the lid to allow access to atmospheric air, as the labyrinth organ requires this. A gap of approximately 2-5 cm is sufficient.

Water Parameters

Temperature	22-28 °C
pH	5.0-7.0
General hardness (GH)	2-8 dGH
Carbonate hardness (KH)	1-5 dKH
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	Below 20 ppm

Betta bellica is a soft-water species that thrives in slightly acidic to neutral conditions. In the aquarium, a pH of between 5.0 and 7.0 is acceptable, with a range of 5.5 to 6.5 being ideal for long-term health and for encouraging breeding behaviour. General hardness should be kept low, between 2 and 8 dGH, and carbonate hardness between 1 and 5 dKH. If your local tap water is hard and alkaline, you may need to use reverse osmosis (RO) water or a combination of RO and tap water to achieve suitable parameters.

Temperature should be maintained between 22 and 28 degrees Celsius. A stable temperature in the range of 24-26 degrees Celsius is optimal for everyday keeping, while slightly warmer temperatures of 26-28 degrees Celsius can be used to condition fish for breeding. Avoid sudden temperature fluctuations, as these can stress the fish and increase susceptibility to disease.

As with all aquarium fish, ammonia and nitrite must be maintained at zero at all times. Nitrate should be kept below 20 ppm through regular water changes and appropriate stocking levels. Betta bellica is somewhat more sensitive to poor water quality than the domesticated Betta splendens, so consistency and diligence in water maintenance are important. Weekly water changes of 20-30% are recommended, using water that has been treated to match the tank’s temperature and chemistry.

The use of Indian almond leaves, alder cones, or commercially available blackwater extracts can help to maintain the slightly acidic, tannin-rich conditions that Betta bellica appreciates. These additives also possess mild antifungal and antibacterial properties, which can benefit the overall health of the fish.

Filtration and Equipment

Filtration for a Betta bellica aquarium should prioritise biological efficiency while producing minimal water flow. In the wild, this species inhabits slow-moving streams, and it does not appreciate strong currents in the aquarium. A sponge filter is an excellent choice for tanks up to around 100 litres, providing gentle biological and mechanical filtration without creating excessive water movement. For larger setups, a small internal filter or a hang-on-back filter with an adjustable flow rate can be used, with the output directed against the glass or baffled with a sponge to reduce current strength.

If using a canister filter, choose one rated for the tank volume and fit a spray bar or lily pipe to disperse the flow over a wider area. The goal is to maintain clean, well-filtered water without creating a strong current that would stress the fish or make it difficult for them to maintain their preferred positions in the water column.

Heating is necessary in most climates to maintain a stable temperature within the species’ preferred range. A reliable, thermostatically controlled heater rated for the tank volume should be installed and its accuracy verified with a separate thermometer. Place the heater near the filter outlet to ensure even heat distribution throughout the aquarium.

Lighting should be subdued. Betta bellica is most comfortable and displays its best colouration under low to moderate light levels. If you are growing live plants, choose species that tolerate lower light rather than installing intense lighting that would cause the fish to become shy and washed out. Floating plants, as mentioned in the tank setup section, are invaluable for naturally reducing light intensity at the water surface. If using LED lighting, a dimmer or a timer that allows for a gradual dawn-and-dusk cycle can help to reduce stress.

A secure, tight-fitting lid or cover glass is the single most important piece of equipment for any Betta bellica tank. This species is a persistent jumper, and even small gaps can be exploited. Ensure that all openings for filter pipes, heater cables, and airline tubing are adequately sealed or covered.

Diet and Feeding

Betta bellica is a carnivorous species in the wild, feeding primarily on small invertebrates, insect larvae, and other tiny aquatic organisms. In the aquarium, it should be offered a varied diet that reflects this natural preference. While some individuals can be trained to accept high-quality dried foods such as micro-pellets or granules formulated for carnivorous fish, live and frozen foods should form the staple of the diet.

Excellent live food options include bloodworm (Chironomus larvae), daphnia, brine shrimp (Artemia), mosquito larvae, and small grindal worms. Frozen equivalents of these foods are widely available and are readily accepted by most Betta bellica. Freeze-dried foods can be offered as an occasional supplement but should not be relied upon as a primary food source, as they are less nutritious than their live or frozen counterparts and can cause digestive issues if fed dry without prior soaking.

Feed adult Betta bellica once or twice daily, offering only as much food as can be consumed within a few minutes. Overfeeding should be avoided, as uneaten food will decompose and degrade water quality. A weekly fast day can be beneficial for digestion and overall health, though this is not strictly necessary if portion sizes are well controlled.

When conditioning a pair for breeding, increase the proportion of live foods in the diet and feed slightly more generously. This helps to bring the fish into peak condition and stimulates the development of eggs in the female. Newly hatched fry require very small foods such as infusoria, vinegar eels, or microworms for the first few days, transitioning to baby brine shrimp (Artemia nauplii) as they grow.

Behaviour and Temperament

Betta bellica is a moderately territorial species, particularly between males, but it is generally less aggressive than the domesticated Betta splendens. In the wild, individuals maintain loose territories around areas of dense vegetation, and encounters between males typically involve ritualised displays rather than outright combat. However, in the confined space of an aquarium, aggression can escalate if insufficient space and cover are provided.

Males will display to one another by flaring their gill covers, spreading their fins, and intensifying their colouration. These displays are usually sufficient to establish a hierarchy without physical damage, provided the aquarium is large enough and contains adequate visual barriers and hiding spots. In tanks of 100 litres or more, it is sometimes possible to maintain a pair or even a small group consisting of one male and two or three females, though careful monitoring is essential. In smaller tanks, keeping a single pair is advisable.

Towards other species, Betta bellica is generally peaceful, though it may occasionally nip at fish with long, trailing fins. It is a somewhat shy fish, especially when first introduced to a new environment, and it may spend the first few days hiding amongst vegetation and only emerging to feed. With time and stable conditions, it will become more confident and spend increasing amounts of time in the open, particularly at or near the water surface.

Betta bellica is a surface-oriented fish, spending much of its time in the upper third of the water column. It frequently rises to the surface to breathe atmospheric air using its labyrinth organ, a behaviour that is entirely normal and should not be mistaken for a sign of respiratory distress. It is also an active swimmer by betta standards, moving with a purposeful, gliding motion through the aquarium.

One notable aspect of Betta bellica behaviour is its response to its keeper. Many individuals learn to recognise the person who feeds them and will approach the front of the tank in anticipation. This makes it a rewarding species for aquarists who enjoy interacting with their fish.

Tank Mates

Betta bellica can be kept with carefully chosen tank mates in a suitably sized aquarium, though it is also perfectly content as the sole species in a dedicated setup. When selecting companions, the key considerations are temperament, size, and environmental requirements. Ideal tank mates are peaceful, not overly boisterous, and share Betta bellica’s preference for soft, slightly acidic water. Avoid species that are known fin-nippers, as well as those that are highly active or aggressive, as these will stress the Betta bellica and may provoke defensive aggression. Similarly, avoid very small species that could be viewed as prey.

Good tank mates

Harlequin Rasbora – A peaceful, soft-water schooling fish from the same geographic region that occupies the mid-water column without competing for surface space.
Chili Rasbora – A tiny, non-threatening rasbora that thrives in similar acidic, soft-water conditions, though ensure the tank is large enough that they are not viewed as food.
Kuhli Loach – A peaceful, nocturnal bottom-dweller that occupies a completely different niche and tolerates soft, acidic water well.
Pygmy Corydoras – A small, peaceful catfish that stays near the substrate and coexists well with surface-dwelling species in soft-water setups.
Chocolate Gourami – A soft-water anabantoid that is similarly calm and reserved, making it a suitable companion in larger, well-planted tanks.
Otocinclus – A small algae-eating catfish that is entirely peaceful and tends to ignore other species while grazing on biofilm and algae.
Ember Tetra – A small, peaceful tetra that adds colour to the mid-water zone and does well in the warm, acidic conditions Betta bellica prefers.
Amano Shrimp – Large enough to avoid predation and useful as a clean-up crew, Amano shrimp coexist peacefully with Betta bellica in planted tanks.

Fish to avoid

Tiger Barb – A notorious fin-nipper that would harass Betta bellica relentlessly, causing chronic stress and potential injury.
Betta splendens – Mixing wild bettas with domesticated bettas risks aggression, hybridisation, and competition for surface territory.
Chinese Algae Eater – Becomes increasingly territorial and aggressive with age and may latch onto the flanks of slow-moving tank mates.
Convict Cichlid – Far too aggressive and territorial, especially during breeding, and requires harder, more alkaline water.
Guppy – The flowing finnage of male guppies may trigger aggression from Betta bellica, and guppies prefer harder, more alkaline water.
Oscar – A large, predatory cichlid that would view Betta bellica as food and requires an entirely different setup.
Serpae Tetra – A known fin-nipper that can be persistently aggressive towards slow-moving, long-finned species.

Breeding

Betta bellica is a mouthbrooding species, with the male assuming responsibility for incubating the eggs in his mouth until they hatch – a fascinating reproductive strategy that sets it apart from the bubble-nesting Betta splendens. Breeding Betta bellica in captivity is achievable for the dedicated aquarist, provided the fish are well-conditioned and housed in appropriate conditions.

To prepare for breeding, condition a pair with generous quantities of live and frozen foods for two to four weeks. The breeding tank should be set up as described in the tank setup section, with plenty of vegetation, subdued lighting, and soft, slightly acidic water. A temperature at the upper end of the species’ range, around 26-28 degrees Celsius, can help to stimulate spawning behaviour.

Courtship begins with the male displaying to the female, flaring his gill covers, spreading his fins, and intensifying his colouration. If the female is receptive, she will respond by displaying vertical barring on her body and approaching the male. The pair will engage in a prolonged courtship embrace beneath the surface or near the substrate, during which the female releases eggs in small batches. The male fertilises the eggs as they are released, and the pair then works together to collect the fertilised eggs. The female typically picks up the eggs first and transfers them to the male’s mouth by spitting them towards him.

Once the male has a full complement of eggs in his mouth, he will cease feeding entirely for the duration of the incubation period, which typically lasts between 10 and 14 days. During this time, it is essential to minimise disturbance to the breeding tank. Avoid rearranging decor, performing large water changes, or introducing new fish, as stress can cause the male to swallow or spit out the eggs prematurely.

The male’s buccal cavity will be visibly distended during incubation, and he may be seen making chewing or rolling motions with his jaw as he aerates and repositions the developing eggs. He will typically remain hidden amongst vegetation during this period, emerging only occasionally to breathe at the surface.

After 10 to 14 days, the male releases fully formed, free-swimming fry. The fry are relatively large compared to those of bubble-nesting bettas and are immediately capable of swimming and feeding. Offer the fry infusoria, vinegar eels, or commercially available liquid fry food for the first few days, transitioning to freshly hatched baby brine shrimp (Artemia nauplii) within a week. The fry grow steadily on a diet of brine shrimp and finely crushed flake or micro-pellet food, and should be separated from the adults once they are large enough to be caught, as the parents may eventually view very small fry as food.

Growth rates are moderate, and juvenile Betta bellica typically begin to show adult colouration and sexual dimorphism at around three to four months of age. Maintaining excellent water quality and providing a varied, high-protein diet during the growth phase is essential for producing healthy, well-coloured young fish.

Common Diseases

Betta bellica is generally a hardy species when kept in appropriate conditions, but it can be susceptible to a number of common freshwater fish diseases, particularly when stressed by poor water quality, inappropriate tank mates, or sudden changes in environmental conditions.

Velvet disease (Oodinium) is one of the more commonly encountered ailments in wild bettas. It presents as a fine, gold or rust-coloured dusting on the skin and fins, accompanied by lethargy, clamped fins, and loss of appetite. Velvet is caused by a parasitic dinoflagellate and thrives in warm, poorly maintained water. Treatment involves raising the temperature slightly, dimming the lights (as the parasite is photosynthetic), and administering a copper-based medication following the manufacturer’s instructions. Note that invertebrates such as shrimp are highly sensitive to copper-based treatments, so remove them before dosing.

Ichthyophthirius multifiliis (white spot disease or “ich”) can also affect Betta bellica, presenting as small white cysts on the fins and body. It is highly treatable with commercially available ich medications or by gradually raising the temperature to 30 degrees Celsius for several days to accelerate the parasite’s lifecycle, combined with increased water changes.

Fungal infections, often secondary to physical injuries or bacterial infections, may appear as white, cotton-like growths on the skin, fins, or mouth. These should be treated promptly with an appropriate antifungal medication. Indian almond leaves and other tannin sources have mild antifungal properties and can be used as a preventative measure.

Fin rot, typically caused by bacterial infection in response to poor water quality or physical damage, manifests as fraying, discolouration, or erosion of the fin edges. Improving water quality through more frequent water changes is often sufficient to resolve mild cases, while more advanced infections may require treatment with a broad-spectrum antibacterial medication.

Internal parasites can occasionally affect wild-caught Betta bellica. Symptoms may include weight loss despite normal feeding, white or stringy faeces, and a generally emaciated appearance. If internal parasites are suspected, treatment with an appropriate antiparasitic medication, often containing praziquantel or levamisole, is recommended. Quarantining all new arrivals for at least two to four weeks before introducing them to an established tank is a sound preventative practice.

The best defence against disease in Betta bellica, as with all aquarium fish, is prevention through good husbandry. Maintaining stable, appropriate water parameters, providing a varied and nutritious diet, avoiding overcrowding, and minimising stress will go a long way towards keeping your fish healthy and disease-free.

FAQs

Can I keep Betta bellica in a small bowl or nano tank?

No. Unlike the domesticated Betta splendens, which is itself poorly suited to bowls despite persistent myths, Betta bellica is a larger, more active fish that requires a properly filtered and heated aquarium of at least 75 litres. Small containers cannot maintain stable water parameters or provide the space and cover this species needs to thrive. A well-planted tank of 75-100 litres or more is the minimum for a pair.

Is Betta bellica a bubble-nester like Betta splendens?

No. Betta bellica is a paternal mouthbrooder. The male incubates the fertilised eggs in his mouth for approximately 10 to 14 days, during which time he does not eat. This is a fundamentally different reproductive strategy from the bubble-nesting behaviour seen in Betta splendens and is one of the many features that make wild betta species so fascinating to keep and breed.

Can I keep two males together?

It is generally not advisable in most home aquaria. While Betta bellica is less aggressive than Betta splendens, males are still territorial and will spar with one another. In very large, heavily planted tanks of 150 litres or more with abundant visual barriers, it may be possible, but close monitoring is essential. For most keepers, a single male with one or two females is the safest arrangement.

Does Betta bellica need a heater?

In most climates, yes. Betta bellica requires a stable temperature between 22 and 28 degrees Celsius, ideally around 24-26 degrees Celsius for everyday keeping. Unless your room temperature remains consistently within this range year-round, a thermostatically controlled heater is necessary to prevent potentially harmful temperature fluctuations.

How can I tell male and female Betta bellica apart?

Males are typically more colourful than females, with more intense bronze-green iridescence and slightly more extended fin tips, particularly on the anal and caudal fins. Females tend to be somewhat plainer in colouration and may display a more rounded belly when in breeding condition. Males also tend to be slightly larger and more slender than females of the same age. The differences can be subtle in young fish but become more apparent as they mature.

Betta simorum – The closest relative of Betta bellica and a fellow member of the bellica species group, sharing similar care requirements and breeding behaviour.
Betta splendens – The most widely kept betta species, useful as a point of comparison for understanding the differences between wild and domesticated bettas.
Chocolate Gourami – A soft-water anabantoid with overlapping habitat requirements, making it an interesting companion species or alternative for a Southeast Asian biotope.
Betta coccina – A popular wild betta from a different species group, offering a useful comparison in terms of size, care, and breeding strategy.
Harlequin Rasbora – A classic Southeast Asian community fish that makes an excellent tank mate for Betta bellica and shares its preference for soft, acidic water.